Assembly for centrifugal blowers and the like

ABSTRACT

An improved rotor and shaft assembly for a centrifugal blower, compressor, or the like that includes a shaft constructed from a material having a first coefficient of thermal expansion and a rotor located on the shaft and constructed from a material having a second coefficient of thermal expansion that is greater than the first coefficient of thermal expansion. Abutments are provided on the shaft that engage the rotor hub to limit the thermal expansion of the rotor in the axial direction to the same expansion as that of the shaft and to convert any excess axial thermal expansion of the rotor into an inwardly deformation of the hub, whereby, the hub more tightly engages the shaft. The arrangement permits the rotor to be slipped onto the shaft during assembly and to be slipped off the shaft during disassembly while at the same time providing for the operation of the blower or compressor at elevated temperatures without loosening of the rotor on the shaft.

United States Patent 1191 Herrick AND THE LIKE ASSEMBLY FOR CENTRIFUGAL BLOWERS 1451 July 23, 1974 Primary ExaminerHenry F. Raduazo [75] Inventor: David Burton Herrick, Connersville, Attorney Agent or Firm-Roy Van wmkle Ind. [73] Assignee: Dresser Industries Inc., Dallas, Tex. [57] ABSTRACT An improved rotor and shaft assembly for a centrifu- [22] Flled' July 1972 gal blower, compressor, or the like that includes a [21] Appl. No.: 276,807 shaft constructed from a material having a first coefficient of thermal expansion and a rotor located on the shaft and constructed from a material having a second '8 415/ coefficient of thermal expansion that is greater than [58] Fieid I53 LK 416/244 the first coefficient of thermal expansion. Abutments 416/244 f 415/199 A are provided on the shaft that engagethe rotor hub to limit the thermal expansion of the rotor in the axial [56] References Cited direction to the same expansion as that of the shaft and to convert any excess axial thermal expansion of UNITED STATES PATENTS the rotor into an inwardly deformation of the hub, 1,886,414 11/1932 Meyer 287/52 whereby, the hub more tightly engages the shaft. The 2,177,924 10/1939 Buckwalter 416/244 arrangement permits the rotor to be Onto the 2,438,866 3/1948 Rockwell et al. 416/244 Shaft during assembly and to be Slipped Off the Shaft during disassembly while at the same time providing ee for the operation of the blower or compressor at ele- FOREIGN PATENTS OR APPLICATIONS vated temperatures without loosening of the rotor on 287,964 10/1915 Germany 416/201 t shaft- 74,422 7/l9l8 Austria 4l6/l94 112,883 4/1929 Austria 416/244 2 Clams 3 Drawmg Flgures I4 L I6 l 2 "X" 1 22 so 32 3a 42 24 I8 3 l I 20 W a 2 Pmmmmza w I 3.825.366

SHEET 1 W 2 FIG.-I

1 ASSEMBLY FOR CENTRIFUGAL BLOWERS AND THE LIKE BACKGROUND OF THE INVENTION This invention relates generally to rotor and shaft assemblies for centrifugal blowers, compressors, and the like. More particularly, but not by way of limitation, this invention relates to an improved rotor and shaft assembly wherein the rotor will not become loose on the shaft even during operation of the compressor or blower at elevated temperatures.

The art is replete with schemes and arrangements for preventing loosening of rotors on shafts where elevated temperatures will be encountered in the operation of the assembly. Despite the fact that for many years, those skilled in the art have made many attempts to prevent the loosening of rotors, no entirely satisfactory arrangement has been found. Perhaps the most common scheme utilized to prevent the rotor from becoming loose is to provide an interference fit between the rotor and shaft and to press the rotor upon the shaft with great force. This scheme is not entirely satisfactory in that it is difficult to assemble the rotor on the shaft during the original manufacturing of the blower and very difficult to disassemble the rotor and shaft and replace the rotor when it becomes necessary in maintenance operations performed upon the compressor or blower away from the factory.

It will be apparent to those skilled in this art, that the ability to retain the rotor on the shaft without loosening during elevated temperature operations is extremely important in high speed compressors and blowers. The loosening of the rotor on the shaft has become more critical as rotating speeds have increased. Should the rotor become loose on the shaft, vibrations will be imparted to the machine and if the rotor becomes suffi-- ciently loosen, the entire machine can be severely damaged or destroyed.

SUMMARY OF THE INVENTION In view of the foregoing, it is one object of this invention to provide an improved rotor and shaft assembly for compressors, blowers or the like that permits operation of the apparatus at high speeds and elevated temperatures without vibration due to loosening of the rotor.

A further object of the invention is to provide an improved rotor and shaft assembly for compressors, blowers or the like wherein the rotor will remain tight upon the shaft even at elevated operating temperatures.

Still another object of the invention is to provide an improved rotor and shaft assembly for compressors, blowers, or the like wherein the rotor can be easilyinstalled and removed from the shaft.

Still a further object of the invention is to provide an improved rotor and shaft assembly for compressors, blowers, or the like wherein the rotor will more tightly engage the shaft at elevated operating temperatures of the apparatus.

This invention provides an improved rotor and shaft sub-assembly for use in a centrifugal blower, compressor, and the like that comprises: a shaft constructed from material having a first coefficient of thermal expansion and arranged to be journaled in the compressor housing; a rotor located on the shaft and rotating therewith, the rotor being constructed from a material having a second coefficient of thermal expansion greater than the coefficient of thermal expansion of the shaft, the rotor including a hub having a axial bore therethrough sized to slidingly to receive the shaft and forming deformable end portions on the hub; means on the shaft engaging the end portions for initially deforming the end portions into engagement with the shaft and for converting thermal expansion of the rotor in the axial direction into radial deformation of the end portions toward the shaft whereby the rotor tightly engages the shaft at elevated operating temperatures of the compressor' The foregoing and additional objects and advantages of the invention will become more apparent as the following detailed description is read in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a cross-sectional view of a portion of a compressor or blower that includes the improved rotor and shaft assembly constructed in accordance with the invention.

FIG. 2 is an enlarged, fragmentary view of a portion of FIG. 1 showing the rotor and shaft assembly in greater detail.

FIG. 3 is a fragmentary cross-sectional view taken generally along the line 3-3 of FIG. 2, but illustrating a slightly modified version of the rotor and shaft assembly that is also constructed in accordance with the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing and to FIG. l in particular, shown therein and generally designated by the reference character 10 is a centrifugal blower constructed 'in accordance with the invention. The centrifugal blower 10 includes a housing 12 having an inlet 14 and an outlet 16. A shaft 18 extends through the housing 12 and is rotatably located therein by a suitable bearings 20, which are located on each end of the shaft 18. (Only the bearing 20 located at the outlet end of the housing is illustrated in FIG. 1.) Suitable seals 22 and 24 are located in the housing at each end of the shaft 18.

First and second rotors 26 and 28, respectively, are located on the shaft 18 in spaced relationship. Relative rotation between rotor 26 and the shaft 18 is prevented by a key 30 that is located in a keyway 32 formed in the shaft 18 and in the rotor 26. The rotor 28 is prevented from rotating relative to the shaft 18 by a key 34 that is located in a keyway 36 formed in the shaft 18 and the rotor 28.

A labryrinth-type seal 38 encircles the shaft 18 and is located between the rotors 26 and 28. The seal 38 functions both to form a seal with the housing 12 to prevent communication between the rotors 26 and 28, except through prescribed passageways, and to maintain the spaced relationship of the rotors 26 and 28.

To prevent axial movement of the rotors 26 and 28 and the seal 38 along the shaft 18, a threaded nut 40 is threadedly connected to the shaft 18 and in engagement with the rotor 26. To prevent movement of the rotors 26 and 28 and the seal 38 in the other direction along the shaft 18, the rotor 28 is engaged by a second threaded nut 42 which is threadedly connected with the shaft 18 near the inlet end of blower 10.

Referring now to the enlarged view of FIG. 2, it can be seen that the rotor 28 is provided with a bore 44 that extends through a hub portion 46 of the rotor. The bore 44 is sized to slidingly receive the shaft 18 thus eliminating the necessity for pressing or otherwise forcing the rotor 28 on the shaft 18. As constructed, the hub 46 provides relatively flexible end portions 48 and 50 for purposes which will be described hereinafter. To further increase the flexibility of the end portions 48 and 50, a pair annular grooves 52 and 54 are formed in the bore 44 adjacent to the end portions 48 and 50, respectively.

As can be clearly seen in FIG. 2, the nut 42 provides.

can be adjusted on the shaft 18 to impose a force on the rotors 26 and 28 deforming the relatively flexible end portions 48 and 50 on the rotor 28 and the end portions (unnumbered) on the rotor 26 inwardly into tight engagement with the shaft 18. Due to the size of the bores in the rotors 26 and28, they can be slipped easily onto the shaft 18 during assembly. However, the imposition of inwardly directed radial forces by means of the nuts 40 and 42 secures the rotors 26 and 28 to the shaft 18 to prevent movement of the rotors 26 and 28 relative to the shaft 18.

The rotors 26 and 28 are constructed from a material having a coefficient of thermal expansion that is greater than the coefficient of thermal expansion of the shaft 18. For example, the shaft 18 may be constructed from steel while the rotors 26 and 28 installed thereon may be constructed .from aluminum, brass, or an alloy thereof. Also, the rotors should be constructed from a material that is compatible with the fluid flowing through the blower. There are a large number of materials available and a material having the desired compatibility and coefficient of thermal expansion can be obtained without difficulty in most instances.

With the blower 10 operating, the fluids flowing therethrough will, due to the work performed thereon and due to friction, increase the temperature of the housing 12, the shaft 18 and the rotors 26 and 28. Since the rotors 26 and 28 are prevented from expanding axially by the nuts 40 and 42, except to the extent that the shaft 18 can expand, considerable force is imposed on the flexible end portions of the rotors due to the greater coefficient of thermal expansion of the rotors. Accordingly, and while it might seem that the rotors should loosen on the shaft 18 due to expansion of the bore 44, they are, in fact, held more securely to the shaft 18 since the axial expansion of the rotor hubs is converted to a radially inwardly directed force that deforms the flexible end portions of the rotors toward the shaft.

If the rotors 26 and 28 need to be replaced, the blower 10 can be stopped and permitted to cool where upon the rotors will contract axially to a greater extent ened permitting the rotors to be slipped rather easily off the shaft and replaced with new rotors.

Thus, the shaft and rotor assembly constructed in accordance with this invention provides not only a means for preventing vibration and loosening of the rotors on the shaft during the operation of the blower at elevated temperatures, but also provides the advantage of ease in disassembly and assembly of the rotors on the shaft 18. Also, the rotor and shaft assembly of this invention can be manufactured at a lower cost because the rotors can be manufactured to somewhat greater tolerances than rotors which must be forced onto the shaft.

DESCRIPTION OF THE MODIFICATION OF FIG. 3

shown in FIG. 2. While four slots 156 are illustrated, it

will be apparent that as many or as few slots may be formed therein as desired to obtain the necessary flexibility of the end portions. 8

Although not shown, it will be understood that similar slots may be provided in the end portion of the modified rotor that corresponds to the end portion 48 of the rotor 28 as well as in either or both end portions of the rotor 26.

It will be understood that the foregoing detailed description is presented by way of example only and many changes and modifications can be made thereto without departing from the spirit and scope of the invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a centrifugal blower, compressor or the like including a housing or stator, an improved rotor and shaft assembly comprising:

a shaft constructed from a material having a first coefficient of thermal expansion and a longituding axis and arranged to be journaled in the housing;

first and second rotors located on said shaft in spaced relationship, said rotors being rotatable with said shaft and being constructed from a material having a second coefficient of thermal expansion greater than said first coefiicient of thermal coefficient, each said rotor including a hub having end portions and an axial bore therethrough sized to slidingly receive said shaft, each said bore having a portion of increased diameter adjacent each said end portion forming relatively flexible, inwardly and outwardly facing radial flanges on said hubs oriented toward said shaft;

seal means on said shaft between said rotors engaging said inwardly facing radial flanges on said rotors and arranged in sealing relationship with the stator;

first abutment means located on said shaft engaging one of said outwardly facing radialflanges; and,

second'abutment means adjustably located on said shaft engaging the other outwardly facing radial compressor. 2. The compressor of claim 1 wherein each said radial flange includes a plurality of radially extending 5 slots to further increase the flexibility of said flanges. 

1. In a centrifugal blower, compressor or the like including a housing or stator, an improved rotor and shaft assembly comprising: a shaft constructed from a material having a first coefficient of thermal expansion and a longituding axis and arranged to be journaled in the housing; first and second rotors located on said shaft in spaced relationship, said rotors being rotatable with said shaft and being constructed from a material having a second coefficient of thermal expansion greater than said first coefficient of thermal coefficient, each said rotor including a hub having end portions and an axial bore therethrough sized to slidingly receive said shaft, each said bore having a portion of increased diameter adjacent each said end portion forming relatively flexible, inwardly and outwardly facing radial flanges on said hubs oriented toward said shaft; seal means on said shaft between said rotors engaging said inwardly facing radial flanges on said rotors and arranged in sealing relationship with the stator; first abutment means located on said shaft engaging one of said outwardly facing radial flanges; and, second abutment means adjustably located on said shaft engaging the other outwardly facing radial flange for initially deforming said radial flanges into engagement with said shaft and for converting thermal expansion of said rotors in the axial direction into radial deformation of said flanges toward said shaft, whereby said rotors tightly engage said shaft at elevated operating temperatures of said compressor.
 2. The compressor of claim 1 wherein each said radial flange includes a plurality of radially extending slots to further increase the flexibility of said flanges. 